A liquid crystal television generally employs a direct illumination-type LED backlight as a light emitting source at the rear of a liquid crystal panel. The direct illumination-type LED backlight is generally formed by an LED lamp and a lens. The lens may enable the LED light to irradiate light uniformly, such that the liquid crystal panel has a uniform luminance, and image quality of the liquid crystal television is further improved.
In the related art, the lens has a small light emitting angle, such that the LED lamp has a small irradiation area. As such, the direct illumination-type LED backlight has a small irradiation area against the liquid crystal panel. To increase the irradiation area of the LED backlight against the liquid crystal panel, manufacturers of the liquid crystal television generally employ a larger number of LED lamps. This, however, increases the manufacture cost, but also increases power consumption of the liquid crystal television.
In a Cartesian coordinate system, an ellipsoid has an equation of x2/a2+y2/b2+z2/c2=1, wherein a, b and c are a random positive constant, and a ratio of a to b to c determines a structure shape of the ellipsoid.